US20070019713A1 - Method of acquiring a received spread spectrum signal - Google Patents
Method of acquiring a received spread spectrum signal Download PDFInfo
- Publication number
- US20070019713A1 US20070019713A1 US10/570,446 US57044606A US2007019713A1 US 20070019713 A1 US20070019713 A1 US 20070019713A1 US 57044606 A US57044606 A US 57044606A US 2007019713 A1 US2007019713 A1 US 2007019713A1
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- Prior art keywords
- signal
- spread spectrum
- fragments
- receiver
- spectrum signal
- Prior art date
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- Granted
Links
- 238000001228 spectrum Methods 0.000 title claims abstract description 30
- 238000000034 method Methods 0.000 title claims abstract description 15
- 239000012634 fragment Substances 0.000 claims abstract description 32
- 230000001413 cellular effect Effects 0.000 claims abstract description 15
- 238000006062 fragmentation reaction Methods 0.000 claims description 11
- 238000013467 fragmentation Methods 0.000 claims description 10
- 230000010267 cellular communication Effects 0.000 claims description 8
- 230000000694 effects Effects 0.000 claims description 2
- 238000004891 communication Methods 0.000 description 15
- 230000000875 corresponding effect Effects 0.000 description 5
- 238000012545 processing Methods 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000002596 correlated effect Effects 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000001427 coherent effect Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 230000012447 hatching Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/13—Receivers
- G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/7073—Synchronisation aspects
- H04B1/7075—Synchronisation aspects with code phase acquisition
- H04B1/7077—Multi-step acquisition, e.g. multi-dwell, coarse-fine or validation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/709—Correlator structure
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/7097—Interference-related aspects
Definitions
- This invention relates to a method of acquiring a received spread spectrum signal, especially a GPS signal, together with a corresponding spread spectrum signal receiver and a cellular telephone comprising a cellular communications transmitter/receiver unit and such a spread spectrum signal receiver.
- such a method, receiver and cellular telephone comprising the steps of: providing a replica signal containing a pseudorandom noise code corresponding to that of the spread spectrum signal; providing a subject signal containing two fragments of the spread spectrum signal initially received during respective time periods between which a further time period elapses; and coherently correlating the replica signal with the subject signal over the two fragments.
- Enabling a spread spectrum receiver to coherently correlation over a signal discontinuity enables such a receiver to better acquire spread spectrum signals, especially if a particularly signal acquisition is inherently difficulat because of say received signal strength, signal interference or multipath distortion.
- the method may further comprise the step of measuring the relative timing of the receipt of the two fragments in which case, the subject signal may be provided containing the two fragments one immediately following the other and the replica signal may be provided with a discontinuity corresponding to the time period elapsed between the respective time periods in which the two fragments are initial received.
- the method may further comprise the step of inserting dummy data, e.g. white noise, in the subject signal between the two fragments wherein the amount of dummy data inserted corresponds to the time period elapsed between the respective time periods in which the two fragments are initial received; and wherein the correlation includes the dummy data.
- dummy data e.g. white noise
- a spread spectrum employing such a method may receive the spread spectrum signal unfragmented but experience subsequent fragmentation inadvertently, occurring prior to correlation due to performance limitations of the receiver. In particular, this may be caused by buffer under run or the inability of a busy processor to service the receiver promptly.
- the latter may be especially relevant to a cellular telephone comprising such a spread spectrum signal receiver together with a cellular communications transmitter/receiver unit if a processor normally used to service the spread spectrum receiver is busy servicing the cellular communications transmitter/receiver unit.
- fragmentation may be intentional and caused by temporarily disabling part of the receiver.
- part of the spread spectrum signal receiver may be intentionally disabled during a period coinciding with activity of the cellular communications transmitter/receiver unit.
- FIG. 1 shows the geographic layout of a cellular telephone network
- FIG. 2 shows mobile cellular telephone MS 1 of FIG. 1 in greater detail
- FIGS. 3 and 4 illustrate two examples of GPS signal acquisition, both in accordance with the present invention, in mobile cellular telephone MS 1 .
- the geographical layout of a conventional cellular telephone network 1 is shown schematically in FIG. 1 .
- the network comprises a plurality of base stations BS of which seven, BS 1 to BS 7 , are shown, situated at respective, mutually spaced geographic locations.
- Each of these base stations comprises the entirety of a radio transmitter and receiver operated by a trunking system controller at any one site or service area.
- the respective service areas SA 1 to SA 7 of these base stations overlap, as shown by the cross hatching, to collectively cover the whole region shown.
- the system may furthermore comprise a system controller SC provided with a two-way communication link, CL 1 to CL 7 respectively, to each base station BS 1 to BS 7 .
- Each of these communication links may be, for example, a dedicated land-line.
- the system controller SC may, furthermore, be connected to a the public switched telephone network (PSTN) to enable communication to take place between a mobile cellular telephone MS 1 and a subscriber to that network.
- PSTN public switched telephone network
- a plurality of mobile cellular telephones MS are provided of which three, MS 1 , MS 2 and MS 3 are shown, each being able to roam freely throughout the whole region, and indeed outside it.
- telephone MS 1 is shown in greater detail comprising a communications transmitter (Tx) and receiver (Rx) 20 connected to a communications antenna 21 and controlled by a communications microprocessor (pp) 22 for communication with the base station BS with which it is registered.
- Tx communications transmitter
- Rx receiver
- pp communications microprocessor
- telephone MS 1 further comprises a GPS receiver (GPS Rx) 23 connected to a GPS antenna 24 .
- GPS receiver receive NAVSTAR SPS GPS signals and pre-processes them, typically by passive bandpass filtering in order to minimise out-of-band RF interference, preamplification, down conversion to an intermediate frequency (IF) and analog to digital conversion.
- IF intermediate frequency
- the resultant, digitised IF signal remains modulated, still containing all the information from the available satellites, and is fed into a memory (not shown) of the communications microprocessor ( ⁇ p) 22 .
- the communications microprocessor is configured to acquire and track GPS signals for the purpose of deriving pseudorange information from which the location of the mobile telephone can be determined using conventional navigation algorithms.
- incoming GPS signals are acquired as illustrated in the following example scenarios:
- mobile telephone MS 1 engages in 2-way communication with base station BS 1 using its communications microprocessor (pp) 22 for a short 10 ms period every second; and further suppose that the user has instructed mobile telephone MS 1 to use its GPS receiver to determine its position.
- pp communications microprocessor
- the GPS receiver receives a GPS RF signal through its antenna continuously, and this signal is pre-processed, sampled and stored. Fragments 1 and 3 are pre-processed, sampled and stored sucessfully, however, at the time when fragment 2 was being pre-processed, sampled and stored, the GPS microcontroller was unable to interface with the communications microcontroller which was busy engageing in the aforementioned periodic 2-way communication with base station BS 1 . Fragment 2 is lost. To accommodate for this, a subject signal is composed of fragment 1 followed immediately by fragment 3 .
- a replica signal is generated containing a pseudorandom noise code corresponding to that of the GPS signal which is intended to be acquired. This signal is then modified to omit a portion of a length corresponding to that of lost fragment 2 . The subject signal and the modified replica signal are then correlated for the purposes of determining whether the target GPS signal has been acquired or not.
- the portion of the memory that would have otherwise stored lost fragment 2 is stuffed with white noise generated by the communications microprocessor.
- the subject signal can then be correlated with an modified replica signal for the purposes of determining whether the target GPS signal has been acquired or not.
- a predefined pseudorandom code or a part of repititions thereof could have been used for stuffing.
- the coherent correlation occurs over a single fragmentation whereas it could of course occur over multiple fragmentations using the underlying principle of the present invention.
- GPS processing is done in the mobile telephone's GPS receiver and communications microprocessor.
- the GPS processing could equally have been distributed, for example, were the GPS RF signal received by the mobile phone's GPS receiver to be recorded and transmitted back to the cellular telephone network's system controller for subsequent processing. In such an event, an inperfect relay of a recorded GPS signal may lead to fragmentation as addressed by the present invention.
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- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Signal Processing (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Mobile Radio Communication Systems (AREA)
- Position Fixing By Use Of Radio Waves (AREA)
- Radio Relay Systems (AREA)
Abstract
Description
- This invention relates to a method of acquiring a received spread spectrum signal, especially a GPS signal, together with a corresponding spread spectrum signal receiver and a cellular telephone comprising a cellular communications transmitter/receiver unit and such a spread spectrum signal receiver.
- In accordance with the present invention, such a method, receiver and cellular telephone are provided, the method comprising the steps of: providing a replica signal containing a pseudorandom noise code corresponding to that of the spread spectrum signal; providing a subject signal containing two fragments of the spread spectrum signal initially received during respective time periods between which a further time period elapses; and coherently correlating the replica signal with the subject signal over the two fragments.
- Enabling a spread spectrum receiver to coherently correlation over a signal discontinuity enables such a receiver to better acquire spread spectrum signals, especially if a particularly signal acquisition is inherently difficulat because of say received signal strength, signal interference or multipath distortion.
- The method may further comprise the step of measuring the relative timing of the receipt of the two fragments in which case, the subject signal may be provided containing the two fragments one immediately following the other and the replica signal may be provided with a discontinuity corresponding to the time period elapsed between the respective time periods in which the two fragments are initial received.
- Alternatively, the method may further comprise the step of inserting dummy data, e.g. white noise, in the subject signal between the two fragments wherein the amount of dummy data inserted corresponds to the time period elapsed between the respective time periods in which the two fragments are initial received; and wherein the correlation includes the dummy data.
- A spread spectrum employing such a method may receive the spread spectrum signal unfragmented but experience subsequent fragmentation inadvertently, occurring prior to correlation due to performance limitations of the receiver. In particular, this may be caused by buffer under run or the inability of a busy processor to service the receiver promptly. The latter may be especially relevant to a cellular telephone comprising such a spread spectrum signal receiver together with a cellular communications transmitter/receiver unit if a processor normally used to service the spread spectrum receiver is busy servicing the cellular communications transmitter/receiver unit.
- Alternatively such fragmentation may be intentional and caused by temporarily disabling part of the receiver.
- Again, in the context of a cellular telephone comprising such a spread spectrum signal receiver together with a cellular communications transmitter/receiver unit, part of the spread spectrum signal receiver may be intentionally disabled during a period coinciding with activity of the cellular communications transmitter/receiver unit.
- The present invention will now be described, by way of example only, of an embodiment of a mobile cellular telephone comprising a GPS receiver for use in a cellular telephone network with reference to the accompanying schematic drawings in which:
-
FIG. 1 shows the geographic layout of a cellular telephone network; -
FIG. 2 shows mobile cellular telephone MS1 ofFIG. 1 in greater detail; and -
FIGS. 3 and 4 illustrate two examples of GPS signal acquisition, both in accordance with the present invention, in mobile cellular telephone MS1. - The geographical layout of a conventional
cellular telephone network 1 is shown schematically inFIG. 1 . The network comprises a plurality of base stations BS of which seven, BS1 to BS7, are shown, situated at respective, mutually spaced geographic locations. Each of these base stations comprises the entirety of a radio transmitter and receiver operated by a trunking system controller at any one site or service area. The respective service areas SA1 to SA7 of these base stations overlap, as shown by the cross hatching, to collectively cover the whole region shown. The system may furthermore comprise a system controller SC provided with a two-way communication link, CL1 to CL7 respectively, to each base station BS1 to BS7. Each of these communication links may be, for example, a dedicated land-line. The system controller SC may, furthermore, be connected to a the public switched telephone network (PSTN) to enable communication to take place between a mobile cellular telephone MS1 and a subscriber to that network. A plurality of mobile cellular telephones MS are provided of which three, MS1, MS2 and MS3 are shown, each being able to roam freely throughout the whole region, and indeed outside it. - Referring to
FIG. 2 , telephone MS1 is shown in greater detail comprising a communications transmitter (Tx) and receiver (Rx) 20 connected to acommunications antenna 21 and controlled by a communications microprocessor (pp) 22 for communication with the base station BS with which it is registered. - In addition to the conventional components of a mobile telephone, telephone MS1 further comprises a GPS receiver (GPS Rx) 23 connected to a
GPS antenna 24. When operative, the GPS receiver receive NAVSTAR SPS GPS signals and pre-processes them, typically by passive bandpass filtering in order to minimise out-of-band RF interference, preamplification, down conversion to an intermediate frequency (IF) and analog to digital conversion. The resultant, digitised IF signal remains modulated, still containing all the information from the available satellites, and is fed into a memory (not shown) of the communications microprocessor (μp) 22. The communications microprocessor is configured to acquire and track GPS signals for the purpose of deriving pseudorange information from which the location of the mobile telephone can be determined using conventional navigation algorithms. - Such methods for GPS signal acquisition, tracking and position determination are well known, for example, GPS Principles and Applications (Editor, Kaplan) ISBN 0-89006-793-7 Artech House. Also, the design and manufacture of telephones of the type of telephone MS1 are well known and those parts which do not directly relate to the present invention will not be elaborated upon here further.
- In accordance with the present invention, incoming GPS signals are acquired as illustrated in the following example scenarios:
- Referring to
FIG. 2 , suppose as part of mobile telephones MS1 registration with base station BS1, mobile telephone MS1 engages in 2-way communication with base station BS1 using its communications microprocessor (pp) 22 for a short 10 ms period every second; and further suppose that the user has instructed mobile telephone MS1 to use its GPS receiver to determine its position. - Referring to
FIG. 3 , upon said instruction, the GPS receiver receives a GPS RF signal through its antenna continuously, and this signal is pre-processed, sampled and stored.Fragments fragment 2 was being pre-processed, sampled and stored, the GPS microcontroller was unable to interface with the communications microcontroller which was busy engageing in the aforementioned periodic 2-way communication with base station BS1.Fragment 2 is lost. To accommodate for this, a subject signal is composed offragment 1 followed immediately byfragment 3. - As is conventional, a replica signal is generated containing a pseudorandom noise code corresponding to that of the GPS signal which is intended to be acquired. This signal is then modified to omit a portion of a length corresponding to that of lost
fragment 2. The subject signal and the modified replica signal are then correlated for the purposes of determining whether the target GPS signal has been acquired or not. - As example 1 except that instead of composing the subject signal from
fragment 1 followed immediately byfragment 3, the portion of the memory that would have otherwise stored lostfragment 2 is stuffed with white noise generated by the communications microprocessor. The subject signal can then be correlated with an modified replica signal for the purposes of determining whether the target GPS signal has been acquired or not. Instead of generating white noise, a predefined pseudorandom code or a part of repititions thereof could have been used for stuffing. - In the above examples, the coherent correlation occurs over a single fragmentation whereas it could of course occur over multiple fragmentations using the underlying principle of the present invention.
- Alsa, in the above examples, all the GPS processing is done in the mobile telephone's GPS receiver and communications microprocessor. However, the GPS processing could equally have been distributed, for example, were the GPS RF signal received by the mobile phone's GPS receiver to be recorded and transmitted back to the cellular telephone network's system controller for subsequent processing. In such an event, an inperfect relay of a recorded GPS signal may lead to fragmentation as addressed by the present invention.
- From a reading of the present disclosure, other modifications will be apparent to the skilled person and may involve other features which are already known in the design, manufacture and use of GPS receivers and component parts thereof and which may be used instead of or in addition to features already described herein.
Claims (15)
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GBGB0320993.9A GB0320993D0 (en) | 2003-09-09 | 2003-09-09 | A method of acquiring a received spread spectrum signal |
GB0320993.9 | 2003-09-09 | ||
PCT/IB2004/051693 WO2005024453A1 (en) | 2003-09-09 | 2004-09-06 | A method of acquiring a received spread spectrum signal |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US13/089,443 Continuation US8289942B2 (en) | 2004-06-16 | 2011-04-19 | Distributed resource reservation in a wireless ADHOC network |
Publications (2)
Publication Number | Publication Date |
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US20070019713A1 true US20070019713A1 (en) | 2007-01-25 |
US7545853B2 US7545853B2 (en) | 2009-06-09 |
Family
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US10/570,446 Active 2026-04-23 US7545853B2 (en) | 2003-09-09 | 2004-09-06 | Method of acquiring a received spread spectrum signal |
Country Status (8)
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US (1) | US7545853B2 (en) |
EP (1) | EP1664828A1 (en) |
JP (1) | JP4668194B2 (en) |
KR (1) | KR101088553B1 (en) |
CN (1) | CN1849522B (en) |
GB (1) | GB0320993D0 (en) |
TW (1) | TW200519397A (en) |
WO (1) | WO2005024453A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2009095280A2 (en) * | 2008-01-28 | 2009-08-06 | Cambridge Silicon Radio Limited | Integrated signal receiver |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2008059441A1 (en) | 2006-11-14 | 2008-05-22 | Nxp B.V. | A method of acquiring a received spread spectrum signal |
CN102323601B (en) * | 2011-05-27 | 2013-02-06 | 哈尔滨工程大学 | Method for capturing GNSS-BOS (Global Navigation Satellite System-Binary Offset Carrier) modulation signal |
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JP3399414B2 (en) * | 1999-09-14 | 2003-04-21 | 日本電気株式会社 | Transmission / reception circuit, mobile communication terminal using the same, control method therefor, and control program recording medium therefor |
GB0004371D0 (en) * | 2000-02-24 | 2000-04-12 | Koninkl Philips Electronics Nv | GPS receiver and mobile unit incorporating the same |
GB0011761D0 (en) * | 2000-05-16 | 2000-07-05 | Koninkl Philips Electronics Nv | A method of despreading a spread spectrum signal |
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JP4225706B2 (en) * | 2001-06-07 | 2009-02-18 | 三洋電機株式会社 | Discontinuous reception method in mobile communication terminal |
-
2003
- 2003-09-09 GB GBGB0320993.9A patent/GB0320993D0/en not_active Ceased
-
2004
- 2004-09-06 WO PCT/IB2004/051693 patent/WO2005024453A1/en active Application Filing
- 2004-09-06 EP EP04769943A patent/EP1664828A1/en not_active Withdrawn
- 2004-09-06 TW TW093126883A patent/TW200519397A/en unknown
- 2004-09-06 JP JP2006525257A patent/JP4668194B2/en not_active Expired - Lifetime
- 2004-09-06 KR KR1020067004777A patent/KR101088553B1/en active IP Right Grant
- 2004-09-06 US US10/570,446 patent/US7545853B2/en active Active
- 2004-09-06 CN CN2004800258291A patent/CN1849522B/en not_active Expired - Fee Related
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US5151919A (en) * | 1990-12-17 | 1992-09-29 | Ericsson-Ge Mobile Communications Holding Inc. | Cdma subtractive demodulation |
US5550443A (en) * | 1994-08-25 | 1996-08-27 | Samsung Electronics Co., Ltd. | Automatic beam current control circuit for multimode monitor and method thereof |
US5905765A (en) * | 1996-09-27 | 1999-05-18 | Rockwell International | Method of processing error-control coded, frequency-hopped communication signals |
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WO2009095280A2 (en) * | 2008-01-28 | 2009-08-06 | Cambridge Silicon Radio Limited | Integrated signal receiver |
WO2009095280A3 (en) * | 2008-01-28 | 2009-10-01 | Cambridge Silicon Radio Limited | Integrated signal receiver |
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Also Published As
Publication number | Publication date |
---|---|
CN1849522B (en) | 2011-03-30 |
JP4668194B2 (en) | 2011-04-13 |
CN1849522A (en) | 2006-10-18 |
US7545853B2 (en) | 2009-06-09 |
EP1664828A1 (en) | 2006-06-07 |
JP2007505519A (en) | 2007-03-08 |
KR101088553B1 (en) | 2011-12-05 |
KR20060071416A (en) | 2006-06-26 |
TW200519397A (en) | 2005-06-16 |
WO2005024453A1 (en) | 2005-03-17 |
GB0320993D0 (en) | 2003-10-08 |
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